Electronic clinical thermometer

ABSTRACT

A predictive-type electronic clinical thermometer comprises a temperature sensing unit, a measuring unit for measuring elapsed time from the start of measurement and an arithmetic unit. The arithmetic unit performs a predictive operation in order to obtain a corrective value utilizing one selected prediction function at one time from among a plurality of prediction functions in which elapsed measurement time is a variable, each function defining a temperature change up to a final temperature. The arithmetic unit calculates the equilibrium temperature based upon the obtained corrective value and the sensed body temperature. In a case where an unstable temperature rise curve exhibits a transition not covered by the group of standard curves which are defined by the predictive functions, the prediction operation is suspended immediately and the actually measured temperature value is displayed at such time.

RELATED U.S. PATENTS AND PATENT APPLICATIONS

U.S. patent applications directly or indirectly related to the subjectapplication are the following:

U.S. Pat. No. 4,541,734, issued Sep. 17, 1985 by Hideo Ishizaka,entitled Electronic Clinical Thermometer, and Method of Measuring BodyTemperature;

U.S. Pat. No. 4,592,000, issued May 27, 1986 by Hideo Ishizaka, entitledElectronic Clinical Thermometer, and Method of Measuring BodyTemperature;

U.S. Pat. No. 4,574,359, issued Mar. 4, 1986 by Hideo Ishizaka, entitledElectronic Clinical Thermometer, and Method of Measuring BodyTemperature; and

Ser. No. 748,663, filed Jun. 24, 1985 by Hideo Ishizaka, entitledElectronic Clinical Thermometer, and method of Measuring BodyTemperature (now U.S. Pat. No. 4,629,336).

Ser. No. 021,775, filed Mar. 4, 1987 by Yutaka Muramoto, entitledElectronic Clinical Thermometer (now U.S. Pat. No. 4,843,577).

BACKGROUND OF THE INVENTION

This invention relates to an electronic clinical thermometer and, moreparticularly, to a predicting-type electronic clinical thermometer inwhich a displayed temperature reading rapidly attains an equilibriumtemperature even before temperature is sensed in real time.

The advantage of an electronic clinical thermometer which predictstemperature that will be attained at thermal equilibrium is that theequilibrium temperature is displayed at an early stage during the courseof measurement. In an electronic clinical thermometer of this type, theearly display of temperature is expected to follow a gradient curve anda predicted value of equilibrium temperature is determined on the baisof the sensed temperature. This difference value shall be referred to asan "add-on value hereinafter. However, when the detected temperaturedescribes an expected curve, the equilibrium temperature cannot bepredicted or the reliability of the prediction declines significantly.Though it may be contemplated when such a temperature rise curve isdetected, there is very little probalility of success even ifre-measurement is effected, and the reliability of the prediction is loweven if the re-measurement is successful.

SUMMARY OF THE INVENTION

The present invention is presented to solve the drawbacks of the priorart, and an object of the invention is to provide an electronic clinicalthermometer which presents a reliable temperature display in accordancewith the measurement conditions.

According to the present invention, the foregoing objects are attainedby providing an electronic clinical thermometer comprising temperaturesensing means for sensing body temperature, means for measuring elapsedtime from the start of measurement, arithmetic means for obtaining acorrective value at that instant utilizing one selected predictionfunction at one time from among a plurality of the predection functionsin which elapsed measurement time is a variable, each function defininga temperature change up to a final temperature, predictive calculationmeans for calculating the equilibrium temperature based upon theobtained corrective value and the sensed body temperature at thatinstant, evaluating means for evaluating the possibility of establishinga prediction, means for altering the measurement mode to a directreading mode in accordance with the evaluation made by the evaluatingmeans, and display means for displaying a temperature value obtained ina predictive mode or direct reading mode(a mode for displaying theactually measured temperature value).

According to another aspect of the present invention, the evaluatingmeans evaluates the possibility of establishing a prediction based uponthe magnitude of a parameter employed in the prediction function.

In yet another aspect of the present invention, the evaluating meansemploys the measured elapsed time as one evaluating element.

In a further aspect of the present invention, the electronic clinicalthermometer further includes discriminating means for discriminating themeasuring mode in which the thermometer is placed.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the basic construction of anelectronic clinical thermometer according to the present invention;

FIG. 2 is a block diagram illustrating, in some detail, the constructionof the electronic clinical thermometer of FIG. 1 according to anembodiment of the present invention;

FIG. 3 is a front view of a display unit;

FIGS. 4 and 5 are flowcharts indicating a process through whichtemperature is predicted at thermal equilibrium in an armpit of asubject;

FIG. 6 is a graph illustrating a corrective temperature differentialcurve according to an embodiment of the invention;

FIG. 7 is a graph illustrating a predicted temperature transition;

FIG. 8 is a graph indicating a weighting set for an electronic clinicalthermometer used in an armpit;

FIG. 9 is a graph indicating a weighting set for an electronic clinicalthermometer used orally;

FIG. 10 is a graph useful in describing the transition of a predicteddisplay temperature from the start of measurement in an armpit; and

FIG. 11 is a block diagram illustrating the electronic clinicalthermometer in a case where the thermometer comprises a microcomputer.

DETAILED DESCRIPTION

Reference will now be made to the block diagram of FIG. 1 showing thebasic construction of an electronic clinical thermometer according tothe present invention. The electronic clinical thermometer basicallycomprises a temperature measurment unit 1, which detects the temperatureof the region where the measurement is performed and producestemperature signals, a prediction operation unit 2 which normallyperforms a prediction operation for obtaining the equilibriumtemperature and in time produces a temperature detected signal when apredetermined situation is detected by the unit 2, and a display unit 3which displays the temperature data.

The temperature measuring unit 1 comprises circuitry having atemperature responsive element such as a thermistor for real-timetemperature measurement of a part of the human body.

The arithmetic unit 2 comprises circuitry for predicting the temperatureat thermal equilibrium. For this purpose it monitors, substantiallycontinuously, a detected signal 11 produced by the temperature measuringunit 1. At first, the unit 2 determines conditions for startingprediction, and subsequently predicts the temperature to be attained atthermal equilibrium constantly at short time intervals using the latestinformation, such as time signal obtained from an internally providedelapsed time measurement function, as well as signal 11 continuouslyprovided by the temperature measurement unit 1, continuously evaluatingthe suitability of the prediction and concurrently executing weightingprocessing so that the displayed value of predicted temperature willshow a smooth transition. The unit 2 delivers a resulting predictionsignal 12 to the display unit 3 substantially continuously until thermalequilibrium is attained. The above mentioned prediction operation issuspended when a decision is made that the temperature signal is notapplicable for the prediction, and instead, the temperature signal isdelivered to the display unit 3.

The display unit 3 displays a predicted equilibruim temperature ordetected temperature. Also, the display unit 3 also provides a functioninforming the user which measurement mode is in operation.

FIG. 2 is a block diagram illustrating in some detail the constructionof an embodiment of an electronic clinical thermometer according to thepresent invention. In FIG. 2, like reference numerals denote like orcorresponding parts in the electronic clinical thermometer of FIG. 1. Itshould be noted that the figure is a functional block diagram whichshows functions which are performed by the stored program fixed in a ROMof a microcomputer. By reading the description thereof givenhereinafter, those skilled in the art will be capable of readilyunderstanding thee invention to a degree necessary for working the same.

The temperature measuring unit 1 comprises a temperature responsiveelement 4 such as a thermistor, and a temperature measuring circuit 5.The latter, which receives an electric signal 13 indicative of sensedbody temperature received from the temperature responsive element 4,samples and converts the signal 13 into digital output signals 14, 15indicative of real-time temperature.

The arithmetic unit 2 for predicting temperature comprises a measurementcontrol circuit 7, a time measuring circuit 6, a corrective valuecomputing circuit 8, an adding circuit 9 , a predicted temperaturemonitoring circuit 10 and a signal switch 27. The measurement controlcircuit 7 controls the overall operation of the electronic clinicalthermometer. This is achieved by constantly monitoring the real-timetemperature signal 15 from the temperature measuring circuit 5, andsupplying the time measuring circuit 6 with a clock signal 16 and thecorrective value computing circuit 8 with a control signal 22 whenpredetermined measurement conditions are satisfied. The time measuringcircuit 6 responds to the clock signal 16 by clocking elapsed time fromthe start of measurement, producing a signal 17 indicative of theelapsed time.

The corrective value computing circuit 8 computes and produces a signal18 indicative of a corrective temperature differential (add-on value)for temperature predicting purposes, the value of U being the differencebetween real-time temperature and temperature attained at thermalequilibrium, in accordance with temperature sensed at sampling instantsbased upon an input of the elapsed time signal. The corrective valuecomputing circuit 8 also produces a display corrective value signal 23obtained by weighting the corrective signal 18. The corrective valuecomputing circuit 8 incorporates a function for obtaining the correctivetemperature differential as a function of elapsed time. The functionincludes several parameters which influence the corrective temperaturedifferential. These parameters are set at the initiation of measurement,for example when a control signal 22 from the measurement controlcircuit is first applied to the computing circuit 8, so as to take onspecific values, e.g. values defined such that a temperature rise withelapsed time will be the most likely average temperature change, whichis obtained statistically in advance by an actual measurement. As willbe described later, the corrective value computing circuit 8 has threefunctions, The first is to compute the corrective temperaturedifferential corresponding to the elapsed time signal 17 input thereto,the output signal 18 being indicative of the computed value. The secondfunction is to alter, upon receiving a negative feedback control signal20 from the predicted temperature monitoring circuit 10, the values ofthe parameters which influence the corrective temperature differential,namely the function for obtaining the corrective temperaturedifferential. The third function is to subject the correctivetemperature differential to a weighting operation which is a function ofelapsed measurement time, as shown in FIGS. 6(a), (b), therebyoutputting the display corrective value signal 23 for the display ofpredicted temperature.

The adding circuit 9 adds the real-time temperature signal 14 and thecorrective signal 18, producing a predicted temperature signal 19, whichis the sum of the real-time temperature T(t) and the correctivetemperature differential U(t) for predicting purposes. The addingcircuit 9 also adds the real-time temperature signal 14 and the displaycorrective value signal 23, producing a predicted display temperaturesignal (Tp) 21, which is the sum of the display corrective value (W(t)U(t) for display purposes and the real-time temperature T(t).

The predicted temperature monitoring circuit 10 monitors the signal 19constantly and decides whether the predicted temperature is withinprescribed limits for a prescribed period of time. The monitoringcircuit 10 outputs the negative feedback control signal 20 to thecomputing circuit 8 when the predicted temperature is outside theselimits, and outputs a display control signal 24 to the computing circuit8 for activating the temperature display when said temperature is withinthe prescribed limits. The predicted temperature monitoring circuit 10also indirectly judges whether the curve of the real-time temperaturesignal 14 is applicable to perform the prediction operation. In caseswhere the decsion is made that the curve is not appropriate, a contactpoint of switch 27 is shifted to the a-side from the b-side; thus themeasurement mode is changed from the prediction mode to the directreading mode (referred to as D-Mode in the drawings).

In the temperature measuring unit 1, the electronic signal 13 from thetemperature responsive element 4 is converted into the signals 14, 15,which are capable of being converted into real-time temperature. Theoutput signal 15 of the temperature measuring circuit 7 immediatelyapplies the clock signal 16 to the time measuring circuit 6 whenpredetermined conditions are satisfied, e.g. when the signal indicatesthat a certain temperature has been exceeded at a temperature change inexcess of a certain value; that is, the electronic clinical thermometerwas brought into contact with the measurement region. At the same time,the control circuit 7 applies the control signal 22 to the correctivevalue computing circuit 8, thereby giving an instruction to begin.

The corrective value computing circuit 8, upon receiving as an input theelapsed time signal 17 from the time measuring circuit 6, computes thecorrective temperature differential for predicting a final temperature,this value being the difference between real-time temperature andtemperature attained at thermal equilibrium. The signal 18 indicative ofthe corrective value is applied to the adding circuit 9. As mentionedabove, the corrective temperature differential is incorporated in thecorrective value computing circuit 8 as a function solely of elapsedtime t including several parameters which influence the correctivetemperature differential.

These parameters are reset at the initiation of measurement, for examplewhen the control signal 22 from the measurement control circuit is firstapplied to the corrective value computing circuit 8 (the signal 22 beingapplied at the same time that the clock signal 16 is applied to themeasurement control circuit 6), so as to take on values which define aspecific temperature change. The correctives value computing circuit 8computes the corrective temperature differential as soon as the elapsedtime signal 17 arrives, and delivers the corrective value signal 18 tothe adding circuit 9.

The adding circuit 9 receives and takes the sum of the real-timetemperature signal and the corrective value signal 18, producing thepredicted temperature signal 19 which is the sum of the correctivetemperature differential and real-time temperature. The signal 19 isapplied as an input to the predicted temperature monitoring circuit 10,which monitors the predicted temperature constantly. When the predictedtemperature is constant for a certain period of time, the monitoringcircuit 10 regards the results of the corrective temperature valuecomputation performed by the computing circuit 8 as being appropriate.In other words, when the predicted temperature is determined to beconstant for a certain time period, the monitoring circuit 10 decidesthat the selection of the computation process, function and parameterapplied in the computation of the corrective temperature value areappropriate. When such is the case, the display control signal 24 isdelivered to the corrective value computing circuit 8 and the predicteddisplay temperature signal 21 is produced and applied to the displayunit 3. When the predicted temperature falls outside, say, a fixed rangeof temperature variation within a predetermined period of time, themonitoring circuit 10 applies the negative feedback control signal 20 tothe corrective value computing circuit 8. The latter responds byimplementing the abovementioned second function thereof, namely byaltering the parameters which influence the corrective temperaturedifferential. Thus, the corrective value computing circuit 8 recomputesthe corrective temperature differential, conforming to the elapsed timesignal 17, based on the altered parameters. The corrective signal 18,which is the result of this computation, is again applied to the addingcircuit 9, the latter producing the predicted temperature signal 19which is monitored by the predicted temperature monitoring circuit 10.

The predicted temperature monitoring circuit 10 repeats the foregoingprocess, with the result being that the weighted predicted temperatureis displayed by the display unit 3.

The foregoing series of process steps, namely the computation of thecorrective temperature differential by the computing circuit 8, theaddition operation performed by the adding circuit 9, the monitoring ofthe predicted temperature by the monitoring circuit 10, the negativefeedback applied from the monitoring circuit 10 to the computing circuit8, and the weighting processing executed when the display is made, areperformed in a short period of time, and the predicted temperaturedisplayed on the display circuit 3 is presented substantiallycontinuously and makes a smooth transition.

FIG. 3 is a front view of the display unit 3 which shows a displayscreen surface, in which 31 denotes a liquid crystal display (LCD)screen. A symbol 32 or 33 is displayed on the LCD screen for incicatingthat the displayed temperature is the predicted equilibrium temperatureor the actual detected temperature. Here the symbol 32 is a sign for thepredicted equilibrium temperature and the symbol 33 is for the sign ofthe detected actual temperature. These symbols are provided for givinginformation on the measurement state(mode) to users; however, thesymbols are not limited to the examples for discriminating themeasurement mode. It is possible to adopt a blinking symblo or to invertblack and white on the LCD screen.

Next will be described the process through which a temperature reachedon attainment of thermal equilibrium is predicted with the embodiment ofFIG. 2. For the discussion, reference will be had to the flowchart ofFIG. 4 and 5 and the corrective temperature differential curvesillustrated in FIG. 6.

The first item requiring discussion is the corrective temperaturedifferential, represented by U. In measuring body temperature, the timeuntil the attainment of thermal equilibrium differs widely dependingupon the thermal characteristics of the clinical thermometer, the stateof the part of the body where the temperture is sensed, and the partitself. If the thermal characteristics of the clinical thermometer arelimited, the various temperature change patterns can be classified intoa number of categories. In other words, placing a limitation upon thethermal characteristics will make it possible to define a number oftemperature change patterns. Two major categories of temperature changeare those resulting from, say, measurement orally and measurement byplacement of the thermometer in an armpit. Several other categories mayalso be conceived, such as temperature change patterns exhibited byadults and children, but these are not particularly useful. Let usconsider measurement of body temperature sensed in an armpit.

With regard to oral measurement, it may be conceived in the same mannerwith the exception that sets of parameters are different from those foran armpit.

It is known from measurement of armpit temperature for a wide variety ofcases that approximately ten minutes is required for attainment ofthermal equilibrium. Let U* represent the difference between temperatureTe at thermal equilibrium and a temperature T during measurement. Uponinvestigation, it is found that U* is expressed with good accuracy bythe following formula:

    U(t)*=Te-T(t)=αt+β+C(t+γ)                 (1)

where:

U*: difference between equilibrium temperature and temperature duringmeasurement

t: time from beginning of measurement

C: variable parameter

α, β, γ: constants in conformance with measurements taken under constantconditions.

In particular, for measurement of body temperature in an armpit, thefollowing holds with good regularity:

    U*=-0.002t+0.25+C(t+1).sup.-0.6 (2≦C≦12)     (2)

where t is measured in seconds and U* in degrees Centigrade.

When U* in Eq. (2) is replaced by U and the value of the parameter isvaried from C=2 to C=12, the curves shown in FIG. 4 are the result. Thereason for replacing U* with U is that the equilibrium temperature Tecorresponds to a predicted temperature Tp as far as execution of theprediction process is concerned. In other words, the correctivetemperature differential U during the prediction process is given by thefollowing equation: ##EQU1##

FIGS. 4 and 5 are flowcharts of an algorithm describing the processingfor temperature measurement as carried out by, say, the arrangementillustrated in the block diagram of FIG. 2.

With the start step 100, power is introduced to the system to actuatethe temperature measuring circuit 5 (FIG. 2), upon which the processmoves to a temperature measurement step 101. In this step, the signal 15from the temperature measuring circuit 5 is monitored by the measurementcontrol circuit 7. In decision steps 102, 103 it is decided whether ornot a measurement of body temperature is to be performed. Specifically,in step 102, it is decided whether a predetermined temperature, say atemperature of 30° C. has been exceeded Step 103 decides whether thetemperature rise is equal to or greater than 0.1° C. per second.

Both of these decisions are executed by the measurement control circuit7. If an affirmative decision is rendered in both cases, then theprocess moves to a step 104 for reset start of the time measurementcircuit 6.

In step 104, a counter in the time measuring circuit 6 for measuringelapsed time is reset by the first clock signal 16 generated by themeasurement control circuit-7 and, at the same time, an elapsed timemeasurement begins in step 105. Step 106 is a decision step which callsfor waiting a certain period of time until a subsequent temperatureprediction step takes on practical meaning. For example, the systemwaits in standby for ten seconds until start of a computation for acorrective temperature. The reason is that the accuracy of temperatureprediction is extremely poor, and would give unsatisfactory results, fora period of less than ten seconds.

When measured results are available for an elapsed time of ten secondsor more, the measurement control circuit 7 produces the control signal22, which executes an initial setting step 107. In this step, theparameter C of the arithmetic expression incorporated in the correctivetemperature value computing circuit 8 is set to a value having thehighest probability of leading to a temperature prediction at thermalequilibrium, this being obtained statistically by performing actualmeasurements in advance.

In the embodiment, C=7 in step 107. Next, step 108 calls for setting 0to a counter N which is provided for high probability of the prediction.

In step 9 flag FLP is reset because prediction has not yet beenestablished and prediction mode (P-MODE) is displayed on the displayunit 3. Next, step 110 calls for determining whether elapsed time t isin excess of a predetermined time t1. Here, the predetermined time t1 isdefined to be time within which prediction should be able to beestablished in the course of ordinary measurement. If it is not judgedthat prediction is established during this predetermined time period, itis judged that the curve shows unstable factors, thereby terminating theprediction operation. In view of the characteristics of the temperaturerise course, the predetermined time t1 for the measurement in the armpitis 100 seconds, and that for oral measurement 70 seconds. Immediatelyafter measurement, such time duration is not sufficient to show a stabletemperature rising curve. A computation of the corrective temperaturevalue within the computing circuit 8 is performed, and accordingly, thecorrective value signal 18 is delivered to the adding circuit 9. Then,the process moves to step 113 to perform the computation thatcorresponds to Equation (3).

The first computation gives as a result a point on the curve marked C=7in FIGS. 6 and 7 and on the curve marked C=7 in FIG. 7. Accordingly, fort=11 sec, we have U=1.77° C. This is applied to the adding circuit 9 asthe corrective value signal 18.

Adding step 114 calls for the adding circuit 9 to add the real-timetemperature signal 14 and the corrective value signal 18 and deliver thesum to the predicted temperature monitoring circuit 10 as the predictedtemperature signal 19. For example, since U=1.77° C. in the presentexample, and if T(11)=34.86° C. Tp=36.63° C. will be applied to themonitoring circuit 10 by the adding circuit 9 upon performing theaddition Tp=T(11)+U(11). The monitoring circuit 10 will receive twovalues of the predicted temperature Tp at a certain time interval forthe same value of C. In a decision step 115, therefore, the predictedtemperature Tp is investigated for any increase or decrease from onearrival to the next.

Three decisions are capable of being rendered in step 115 by comparingthe change in Tp with a certain value a. If the decision is dTp/dt≧a,this indicates that an equilibrium temperature higher than thatpredicted at the present time can be expected. Accordingly, the processmoves to a step 111 to increase the value of the parameter C.

If the decision is dTp/dt≦-a, then this indicates that an equilibriumtemperature lower than that predicted at the present time can beexpected. The process therefore moves to a step 124 to decrease thevalue of the parameter C. For |dTp/dt|<a, the indication is that theequilibrium temperature predicted at the present time lies within limitswhere said temperature can be regarded as being approximately equal tothe equilibrium temperature predicted previously. Therefore, theselected temperature prediction function is deemed to be on the righttrack for a real-time temperature measurement, and processing moves tostep 116 for forming a predicted display temperature.

In steps 124,127, the negative feedback control signal 20 from themonitoring circuit 10 is applied to the corrective value computingcircuit 8 to change the parameter C. The value of the new parameter C ischecked within the computing circuit 8 in accordance with steps 126, 129and is used as the parameter in step 113 for recomputation of thecorrective value providing that upper and lower limits are not exceeded,i.e. provided that the increased parameter C does not exceed the setupper limit value 12 in decision step 129, and that the decreasedparameter C does not fall below the set lower limit value 2 in decisionstep 126.

However, in cases where the parameter C exceeds the upper limit value 12in decision step 129, and falls below the set lower limit value 2 indecision step 126, it is decided that the real-time temprature signal 14is outside predictable limits of the prediction function. In otherwords, there is no probability of a coincidence of the curves drawn bythe prediction function and the real-time temperature-signal. Curves (a)and (b) in FIG. 6 depict curves with no probability of coincidence. Thecurve (a) indicates an equilibrium temperature higher than that which itis possible to reach and the curve (b) indicates that an equilibriumtemperature lower than that which it is possible to reach. In eithercase, therefore, it is meaningless to display the predicted equilibriumtemperature, flag FLP is reset in step 122, direct reading mode isindicated on display unit 3, and the real-time temperature is displayedin step 123.

It should be noted that the curves (a) and (b) should not be restrictedto the form depicted in the drawing. They may take any form.: Wheneverdecision steps in 126 or 129 make a decision that the curves are exceedthe conditions, it denies absolutely the possibility of coincidencebetween the curve and the prediction function. Curves (a) and (b) areconceived to show typical curves for which it is impossible to perform aprediction of the equilibrium temperature. Therefore, to evaluate thecurves (a) and (b) are equivalent to evaluate any and all temperaturerise curves which do not fall within the range of a group of standardcurves prepared as prediction functions. With regard to a curve (c), nodecision has been made that it exceeds conditions in step in 126, 129.No decision has thus been made on the possibility of coincidence becausethere remains some possiblity for establishing prediction at thatinstant.

Now, control goes to step 116 and calls for adding "1" to the counter Nbecause the predictive equilibrium temperature at two successivesampling instants are found to be in coincidence. That is, at thisinstant, it may be supposed that a part of both the curve of real-timetemperature and that of drawn by the selected prediction functioncoincide. In decision step 117, the magnitude of the corrective valueU(t) is evaluated. When U(t)<0, the measurement mode is changed to thedirect reading mode because there is no value to be added on. Suchsituation will be produced after considerable measurement time haselapsed. More precise measurement can be expected by placing thethermometer in the state of direct reading mode When, U(t)≧0.1 the valueof the counter N is examined in step 118. Where the corrective valueU(t) is larger or equal 0.1, the clinical thermometer exhibits itsgreatest predictive ability. In step 118, if the number of N in thecounter is not larger than 3, the prediction is still uncertain, and theprocessing goes to back to step 110. If the value of the counter N islarger than 3, it indicates that the predictive equilibrium temperatureTp of four successive sampling instants approximately coincide; thusboth the curve of the real-time temperature and the selected predictioncurve are assumed to be largely coincident. Then processing moves tostep 119 and sets FLP at "1", thereby establishing the validity of theprediction. If this is occuring for the first time, a buzzer sound isgenerated. It is needless to say that the establishment of predictionvalidity also may be indicated by setting the counter N to "1".

The step 120 calls for weighting (described later) to be performed inorder to form the predicted display temperature. The display step 121calls for the presently prevailing predicted display temperature signal21 to be outputted by the adder 9 so that the predicted displaytemperature at the present point in time may be displayed by the displayunit 3. When step 113 ends, the process returns to the corrective valuecomputation step 101 while the predicted temperature remains displayedon the display unit 3.

Thus, after establishment of the validity of the predicton, the seriesof prediction operations is continued, whereby more precise temperatureprediction is possible in accordance with user's volition. If thecondition 0≦u(t)<0.1 is satisfied, the processing moves to step 120. Atthis stage, the add-on value becomes small, so that the accuracy of theprediction is sharply increased. Thus we can judge that the validity ofthe prediction is established at that stage.

Thus, the predicted temperature is displayed on the display unit, aftersuch processing as rounding to the nearest whole number, only when thecondition |dTp/dt|<a is satisfied. The displayed value is retained untilthe next display step. The processing loops such as steps for arithmeticoperation or display is controlled by the measurement control circuit 7so as to be repeated at a predetermined interval of, say, one second.

Where the curve of the real-time temperature describes curve (c) in FIG.6, the validity of the prediction is not readily established.Temperature rising data shows an unstable transient if poor contact ofthe probe with the skin is maintained for some time, or the probevirtually loses contact with the region. If this kind of situationcontinues for the first predetermined time period T1, a decision Yes isrendered in step 110, and processing moves to step 111 where the stateof the flag FLG has not been set. The measurement state is changed intothe direct reading mode because it cannot expect to correctly measurethe temperature even if the prediction mode is continued in suchmeasurement circumstance. When the setting of flag FLP is confirmed instep 111, processing moves to step 112 where it is confirmed whether thesecond predetermined time period T2 has elapsed or not. By way ofexample, the second predetermined time period T2 is a time period suchthat sufficient measurement time has elapsed since the initiation ofmeasurement that no add-on value is necessary. As will be describedlater, the add-on value becomes 0 when 8 minutes 30 seconds ofmeasurement time has elapsed in the case of armpit measurement, and 6minutes 30 seconds in the case of oral measurement. Accordingly,measurement is changed to the direct reading mode when such condition oftime elapse is satisfied according to the manner of measurement (i.e.oral or armpit measurement). If the user continues measurement after thebuzzer sound is generated, the time T2 will soon expire and, he will seeboth the indication of the direct reading mode as well as themeasurement data.

In the example of FIGS. 3 and 4, the algorithm alters the value of theparameter C in increments or decrements of one. In such case theresolution of the predicted temperature will be on the order of 0.1° C.at about 50 seconds into the prediction computations. To obtain evengreater resolution, therefore, the value of the parameter C should beincremented or decremented by 0.5 in steps 124 or 128. Further, thevalue of a in the decision step 110 need not be constant. It can, forexample, be a function the value of which diminishes with time. Such anexpedient is preferred in view of the fact that the temperaturedifference separating one corrective temperature curve from another inFIG. 6 grows smaller with the passage of time. To compute dTp/dt,obviously various methods are conceivable using a running average orthree values of Tp separated widely in time, so long as there is nosignificant influence upon the accuracy of measurement. In any case,even when the display step 121 is eventually selected as the result ofthe decision in step 115, processing returns to step 115 through thecorrective value computation step 113 and adding step 114 forcomputation of Tp. During the repeated execution of this loop, thecomputation for predicting temperature is regarded as following theactual temperature change. Accordingly, the computed value of thepredicted equilibrium temperature will stabilize and the displayed valuethereof will make a smooth and rapid transition. The corrective value Uwill follow e.g. the curve C=7 in FIG. 7.

At time t=16 sec, the decision rendered in step 115 is dTp/dt≧a, afterwhich the process moves to step 127 where the parameter C is incrementedto 8. On the curve C=8, we will have U=1.63° C. If T=35.20° C. at suchtime, then the result of computation in step 114 will be Tp=36.83° C.Now, in accordance with step 115, two values of the predictedtemperature (i.e. two values taken at a certain time interval), for thesame C (=8), are checked. As long as the change in Tp does not exceed acertain value, the loop which includes the display step, 121 is steppedthrough repeatedly, so that a value of Tp in the neighborhood of 36.8°C. is obtained continuously. As will be described below, weighting atthis time is 36%, so that the substantial display temprature is lowerthan 36.8° C. At time t=53 sec, the program proceeds to the loop decidedby dTp/dt≧a, so that the curve tracked is indicated by C=9. SinceU=0.96° C., T=36.03° C. will now hold, the result of calculation in step120 will be Tp=36.99° C. As will be described below, weighting at thistime is 100%, so that the substantial display temperature is 36.99° C.From this point onward the prediction of temperature proceeds along thecurve C=9. The value of Tp being rounded off is as indicated by thedashed line 200 in FIG. 7.

Thus, as described hereinabove, body temperature which will prevail atthermal equilibrium is predicted and displayed substantiallycontinuously.

In the algorithm illustrated in FIGS. 4 and 5, the parameter C isintially set to the value of 7 in step 107. By doing so, however, theremay be instances where the displayed value diminishes with time, owingto the method of processing or the way in which the value of a isselected in the decision step 115 for monitoring the predictedtemperature. To give the operator a more natural impression oftemperature transition, therefore, C can be set initially to 2 in step107, so that the displayed value will, in general, rise with the passageof time. Thus, parameter selection causes the equilibrium temperature tobe rapidly approached with respect to elapsed measurement time.

FIGS. 9 and 10, illustrate a change in weighting with respect to elapsedmeasurement time, in which FIG. 9 is a graph of weighting set fortemperature measurement in an armpit and FIG. 10 is a graph set fortemperature measurement taken orally. These graphs are example ofweighting characteristics determined statistically and on the basis ofexperience taking into consideration differences in the thermalequilibrium characteristics of the part of the body measured.

Generally, sensed temperature immediately after the thermometer iscontacted with the body exhibits a steep temperature variation. Theabovementioned add-on value for this portion of the temperature curve islarge in magnitude. Until the prediction function selected is anappropriate one, therefore, the add-on value also undergoes adiscontinuous and large-scale variation due to the changing of theprediction function. Consequently, if the add-on value during thisinterval of time were added on as is, the predicted temperature displaywould be unstable and difficult to read. Accordingly, until passage of apredetermined period of time from the start of measurement, thecorrective value computing circuit 8 subjects the add-on value(corrective value signal 18) obtained to weighting having a linearlyincreasing characteristic. For example, if the temperature measurementis taken in the armpit, then weighting having a slope that will raisethe add-on value to 100% is applied until 45 seconds elapse from thestart of measurement. If the temperature measurement is taken orally,then weighting having a slope that will raise the add-on value to 100%is applied until 30 seconds elapse from the start of measurement.

When the first predetermined time period elapses, the rise in the sensedtemperature becomes more gentle and the add-on value for this portion ofthe curve also falls within a suitable range. From this point onward,the rapidity at which the prediction converges toward the finaltemperature and the accuracy of the prediction become important factors.Accordingly, when the first predetermined time period elapses, thecorrecting value computing circuit 8 subjects the add-on value (thecorrective value signal 18) obtained to 100% weighting until the elapseof a second predetermined time period. This is equivalent to notexecuting weighting processing. By way of example, the secondpredetermined time period is 348 seconds (six minutes and 24 seconds)from the start of measurement in case of armpit measurement and 256 sec(four minutes and 16 seconds) from the start of measurement in case oforal measurement.

When the second predetermined time period elapses, the sensedtemperature itself falls within a range close to the equilibriumtemperature. When this much time has passed, the merits of performing aprediction diminish and it is better to shift to a direct display-typefunction. Accordingly, when the second predetermined time periodelapses, the corrective value computing circuit 8 subjects the add-onvalue (corrective value signal 18) to weighting having a linearlydecreasing characteristic until passage of a third predetermined timeperiod. By way of example, for measurement taken in an armpit, weightinghaving a slope for a weighting transition of 100% to 0% is performedfrom a point 384 seconds after the start of measurement until a point511 seconds after the start of measurement (8 minutes and 31 seconds).For measurement taken orally, weighting having a slope for a weightingtransition of 100% to 0% is performed from a point 256 seconds after thestart of measurement until a point 384 seconds after the start ofmeasurement (6 minutes and 24 seconds). The continuity of the displayedtemperature is maintained by not suddenly applying 0% weighting in thistime interval. In other words, a smooth and gradual transition is madeto the direct reading state by gradually reducing the percentageoccupied by the add-on value.

When the third predetermined time period elapses, the sensed temperatureitself indicates the thermal equilibrium temperature. From this pointonward, therefore, the add-on value is 0. The electronic clinicalthermometer of the present embodiment thenceforth functions as aconventional direct reading-type clinical thermometer and temperaturecan be measured until the user is satisfied. The displayed temperatureis thus enabled to make a smooth transition with the passage of time.The requirement for a rapid display of predicted temperature as well asan accurate direct reading of temperature is thus satisfied.

FIG. 10 is a graph useful in describing the transition of a predicteddisplay temperature from the start of measurement in an armpit. By wayof example, the prediction function associated with a parameter C=8being selected at the present point in time is prescribed at thecorrective value signal 18, as illustrated in FIG. 10. It will beunderstood that when the selected parameter C=8 matches the rising curveof the real-time temperature signal 14, the predicted temperature signal19 rapidly attains the thermal equilibrium temperature. Accordingly, ifan appropriate parameter selection is always made, the predictedtemperature signal 19 will be displayed, whereby an ideal temperaturedisplay is obtained. However, since the initially set value of theparameter C is a statistically determined value having the highestprobability of leading to a temperature prediction at thermalequilibrium, the parameter C will not necessarily match the real-timetemperature signal 14 at an early time. When matching is not achieved,the predicted temperature Signal 19 will probably make an unstabletransition due to the changeover of the prediction function. Forexample, there are cases where the predicted temperature signalinitially exhibits a value higher than the equilibrium temperature andthen gradually decays, and cases where the predicted temperature signalis initially quite low and then rises sharply. Accordingly, elapsed-timeweighting shown in FIG. 6(a) is applied to the add-on value U(t) of theprediction function in the time interval from the start of measurementto the instant 45 seconds thereafter. As a result, the corrective valuesignal 23 for display purposes is calculated in accordance with U'=W(t)U(t), the signal starting at a value of 0 and then gradually rising. Inthe time interval from the start of measurement until 45 secondsthereafter, therefore, the display temperature signal 21 is smaller thanthe predicted temperature signal 19, rises smoothly and quickly attainsthe equilibrium temperature before the real-time temperature signal 14.Forty-five seconds after the start of measurement, a continuous,accurate and stable display of equilibrium temperature is achieved.

With the present state of the art, a hardware arrangement of the kindshown in FIG. 11, which makes use of a microcomputer, is well suited forimplementing the complicated temperature prediction algorithm of thekind shown in FIGS. 3 and 4. Elements in FIG. 11 similar to those shownin FIG. 2 are designated by like reference numerals.

In FIG. 11, the temperature signal 14 from the temperature measuringcircuit 5 is applied as an input to a processor 154 constituting part ofthe arithmetic unit 2. The temperature signal 15 from the temperaturemeasuring circuit 5 is applied as an input to a temperature thresholdvalue sensing circuit 150 and to a temperature change sensing circuit151. The sensing circuit 150, which executes step 102, comprises acomparator for determining whether the temperature T expressed by signal15 has exceeded a threshold temperature Tth, producing a signal 160 whensuch is the case. The temperature change sensing circuit: 151, whichexecutes step 103, determines whether the change in the temperature Twith time, represented by signal 15, has exceeded a predetermined valuek, and produces a control signal 161 when such is the case.

The control signals output 161 of the temperature change sensing circuit151 is connected to a measurement control circuit 152. The latterproduces an output 162 applied to a clock signal generating circuit 153,and an output 163 applied to the processor 154. The measurement controlcircuit 152 responds to the control signal 161 by actuating the clocksignal generating circuit 153, and instructs the processor 154 toexecute the process steps from step 105 onward. The clock pulsegenerating-.circuit 153 produces a clock pulse output 164 supplied tothe processor 154, the latter responding by executing the aforementionedprocessing steps from step 107 onward in e.g. FIGS. 4 and 5. In theillustrated embodiment the processor 154 can be realized in the form ofa single-chip microcomputer.

The display unit 3 in FIG. 9 includes a buzzer circuit 155 for anaudible alarm, as well as a display device 156. The buzzer 155 is forinforming the user of an error condition or % of the fact thatsuitability of a prediction has been detected. The display device 156 isfor displaying the predicted display temperature.

EFFECT OF THE INVENTION

In accordance with the invention as described above, predictivecalculations are performed quickly and effectively if an ordinarytemperature rise curve falls within the range of a group of standardcurves prepared as prediction functions. In case of an unstabletemperature rise curve that exhibits a transition not covered by thegroup of standard curves, the prediction operation is suspendedimmediately and the actually measured temperature value is displayed atsuch time. This is to prevent obtaining an unreliable prediction basedon the unstable curve. Accordingly, this makes it possible to indicatethe correct body temperature value at all times under a wide variety ofbody temperature measurement conditions.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the appended claims.

What is claimed is:
 1. An electronic clinical thermometercomprising:temperature sensing means for sensing body temperature at aprescribed part of a body; means for measuring elapsed time from a startof measurement; memory means for storing weighting factors which areselectable in response to the time elapsed from the start ofmeasurement; arithmetic means for obtaining a corrective value at ameasured elapsed time utilizing one selected prediction function,according to the measured elapsed time, from among a plurality ofprediction functions; predictive calculation means for calculating anequilibrium temperature by adding the obtained corrective value to thesensed body temperature at the measured elapsed time; measuring modesetting means for setting a measurement mode to one of a predictivemeasurement mode and a direct measurement mode, wherein the measurementmode is initially set to the predictive measurement mode and changedover to the direct measurement mode after a predetermined measuredelapsed time; and display means for displaying a temperature valueobtained using the measurement mode in which the thermometer is set. 2.An electronic clinical thermometer according to claim 1, wherein thedisplay means displays the temperature value determined by thepredictive measurement mode and the temperature value determined by thedirect measurement mode in such a manner that it is possible todiscriminate which is being displayed.
 3. An electronic clinicalthermometer comprising:temperature sensing means for sensing bodytemperature at a prescribed part of a body; means for measuring elapsedtime from a start of measurement, and for generating an elapsed timesignal which indicates the measured elapsed time; arithmetic means forobtaining a corrective value at a measured elapsed time utilizing oneselected prediction function at one time from among a plurality ofprediction functions, each prediction function defining a temperaturechange as a function of measured elapsed time, up to a finaltemperature; predictive calculation means for calculating an equilibriumtemperature based upon the obtained corrective value and the sensed bodytemperature at the measured elapsed time used by the arithmetic means todetermine the corrective value; measuring mode setting means for settinga measuring mode of the thermometer; direct reading means for directlyreading the body temperature sensed by the temperature sensing means;evaluating means for evaluating a possibility of establishing aprediction of body temperature; means for changing the-measuring modefrom a prediction measuring mode to a direct reading mode in accordancewith the evaluation made by the evaluating means; and displaying meansfor displaying a temperature value obtained by the measuring mode inwhich the thermometer is set.
 4. An electronic clinical thermometeraccording to claim 3, wherein the evaluating means evaluates apossibility of establishing prediction of body temperature based uponthe magnitude of a parameter used by the predictive calculation means.5. An electronic clinical thermometer according to claim 3, wherein theevaluating means uses measured elapsed time as an evaluating element forevaluating the possibility of establishing prediction of bodytemperature.
 6. An electronic clinical thermometer according to claim 3,wherein the display means further includes means for displaying themeasuring mode in which the thermometer is set.